Regional density surveys exist within protected areas such as Saguaro National Park, but the IUCN's own assessment does not extrapolate them into a single rangewide total, so no honest total-population figure can be given.
What would resolve this A coordinated rangewide census across the full Sonoran Desert distribution, extending the plot-based methods already used inside individual protected areas.
OpenBotany and desert ecologyIUCN Red List of Threatened Species